Thread severing attachment for sewing machine



M. SPINRAD ET AL Dec. 3, 1968 3 ,413,944

THREAD SEVERING ATTACHMENT FOR SEWING MACHINE Filed Oct. 1, 196

S Sheets-Sheet 1 INVENTOR- MRLCOM SP h BY BR E- uoveem,a.

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Dec. 3, 1968 M. SHNRAD ET AL- 3,413,944

THREAD SEVBRING ATTACHMENT FOR SEWING MACHINE Filed Oct. 1, 1965 5Sheets-Sheet 2 WFQI QII Q l W, V r I 33 W/////.// 3 143 MN I I 34 H I 3imu 1 M mniuu FIG ,4 1N ENTOR.

MRI-60M SPI an an BY BRYCE E- nova-magaz- Dec. 3, 1968 M. SPINRAD ET ALTHREAD SEVERING ATTACHMENT FOR SEWING MACHINE Filed Oct. 1, 1965 5Sheets-Sheet 5 INVENTOR.

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THREAD SEVERING ATTACHMENT FOR SEWING MACHINE 5 Sheets-Sheet 4 FiledOct. 1, 1965 FIG. 5

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Dec. 3, 1968 $P|NRAD ET AL 3,413,944

THREAD SEVERING ATTACHMENT FOR SEWING MACHINE Filed Oct. 1, 1965 5Sheets-Sheet 5 INVENTOR.

MHLpoM SVIN RAD I (bRYca E2 HoVERTERpE United States Patent 3,413,944THREAD SEVERING ATTACHMENT FOR SEWING MACHINE Malcom Spinrad and BryceE. Hoverter, Jr., Reading, Pa., assignors to American Safety TableCompany, Inc., Reading, Pa., a corporation of Pennsylvania Filed Oct. 1,1965, Ser. No. 492,200 14 Claims. (Cl. 112252) ABSTRACT OF THEDISCLOSURE Special throat plate apparatus for a sewing machine toprovide simultaneous severance of both needle thread and bobbin threadclose to the undersurface of the work by first snubbing both threadswith a slider against an unheated heatable wire carried by the throatplate at a time when the needle thread take-up lever has risen to aparticular position lower than its topmost position, then severing boththreads by heating the heatable wire after the needle thread take-uplever has completed its rise to draw thread for the next stitch, andthen retracting the snubbing slider. The apparatus can be operatedmanually or in conjunction with an automatic needle positioningmechanism, which latter is described with the illustration of anoperating circuit.

This invention relates to thread severing mechanisms for sewingmachines, and more particularly relates to a mechanism forsimultaneously cutting both the needle thread and the bobbin thread at apoint very close to the outer surface of the material being stitched sothat subsequent trimming of such threads is not required.

In commercial operations utilizing sewing machines for the massproduction of stitched articles, such as in the garment trade, the saleprice of the stitched article produced is necessarily related to thelabor cost involved in producing the same. Accordingly, reductions inthe fabrication time of a stitched article result in the ability to sellsuch articles at a lower price, and labor saving devices are thereforeof great interest to the trade. During the stitching process, it isfrequently necessary to sever the needle and bobbin threads while thefabric being stitched is centrally located relative to the needle, thatis, when the line of stitching does not terminate at or near the edge ofthe fabric.

Generally, in such a case, the work must be displaced from its positionat the end of the line of stitching so that sufiicient of the needle andbobbin threads become available for hand cutting, the work being thenrepositioned in the proper place of starting the next line of stitching.After the stitching operations have all been completed it is thennecessary to trim off all the projecting thread ends so that thestitched article may present a neat and finished appearance. Such athread cutting operation is time consuming and can contribute materiallyto labor costs associated with the production of a particular stitchedarticle.

In order to alleviate this thread trimming problem, attempts have beenmade in the past to provide automatic thread cutting means designed toleave a minimum of thread to be trimmed and which in some cases could beignored. One such thread cutting means has been mounted to the rear ofthe presser foot to cut the thread by a vertical down stroke of acutting edge. This type of apparatus, of course, could only be used atthe edge of a fabric where the fabric is shifted out from under theneedle and behind the vertical cutting device, in order that the cuttingstroke should cut only the thread and not the underlying fabric as well.The vertical cutting devices are therefore of limited use, being helpfulonly in those cases where the line of stitching terminates at the edgeof the stitched. article.

Other mechanical cutting arrangements have been devised which cut thethread by a cutting stroke in a plane parallel to the surface of thefabric being stitched. Such devices can of course be utilized when thefabric is centrally located under the needle without requiring that thefabric be removed from the sewing machine. However, even cutters of thistype generally leave thread ends of undesirable length and the need forsubsequent trimming of the short ends remains. This invention on theother hand provides for cutting of the needle and bobbin threadssimultaneously and very close to the fabric surface, and consequentlyeliminates the need for subsequent trimming.

Previously known hot wire thread cutting devices, as for example thatshown in US. Patent No. 3,191,562 assigned to the assignee of thisinvention, have utilized separate hot wire devices to independentlysever the needle thread and bobbin thread with the needle thread beingsevered by a hot wire carried by a specially constructed presser foot.The present invention eliminates the need for such a special presserfoot and thereby permits sewing machine operation with the standardtypes of presser feet normally employed. Moreover, other thread trimmingdevices have required the use of auxiliary needle thread clampingdevices to prevent dethreading of the needle after severing has beeneffected and stitching has been recommenced. Such clamping devices arenot required with the present invention when utilized in a novel waywith an automatic needle positioning device.

Briefly, our invention accomplishes thread cutting by apparatusincluding a single hot wire associated with the throat plate of thesewing machine which rapidly burns through both the needle and bobbinthreads to be severed. This single hot wire is only energized when sodesired by the sewing machine operator, so that during a normalstitching operation there is no tendency whatever for needle thread andbobbin thread to be prematurely sevcred. Additionally, means are alsoprovided for insuring that the sewing machine may be again immediatelyutilized after a thread cutting operation without having to re-threadthe needle. Accordingly, it is a primary object of this invention toprvoide a novel thread cutting apparatus effective when actuated tosever the needle thread and bobbin thread of a sewing machine very closeto an outer surface of an article being stitched to thereby eliminatethe need for subsequent hand trimming of short thread ends.

Another object of this invention is to provide a novel thread cuttingapparatus for severing the needle thread and bobbin thread of a sewingmachine close to the surfaces of a stitched article by means of anoperator controlled and selectively energizable hot Wire.

Yet another object of this invention is to provide novel thread cuttingapparatus which permits the needle thread and bobbin thread associatedwit-h the sewing machine to be cut simultaneously without displacing thearticle being stitched from the position it occupies at the end of thestitching operation.

A further object of this invention is to provide novel thread cuttingapparatus including means for insuring that the thread cutting operationdoes not unthread the needle of the sewing machine.

The foregoing and other objects of the invention will become clear froma reading of the following specification in conjunction with anexamination of the appended drawings, wherein:

FIGURE 1 is a fragmentary elevational view showing the working end of asewing machine head as seen looking into the front of the presser foot,illustrating one view of the means employed to provide needle threadtension release in order to avoid rethreading of the needle after thethread cutting operation;

FIGURE 2 is an end elevational view of the sewing machine headillustrated in FIGURE 1 illustrating certain organizational details ofthe thread severing mechanism not visible in FIGURE 1;

FIGURE 3 is a rear elevational view of that part of the sewing machinehead which is seen in FIGURE 1 illustrating certain details of themechanical arrangement utilized to provide needle thread tensionrelease;

FIGURE 4 is a view of the apparatus according to the invention as wouldbe seen when viewed along the line 44 of FIGURE 1;

FIGURE 5 is a perspective view of the apparatus for efiecting needlethread tension release illustrated as removed from its mounted positionon the sewing machine head;

FIGURE 6 is a perspective View of the thread severing mechanismdemounted from the sewing machine structure;

FIGURE 7 is an enlarged exploded top perspective view of the throatplate and underlying thread shifting slide device;

FIGURE 8 is -a vertical sectional view through the throat plate of thesewing machine as would be seen when viewed along the line 8-8 of FIGURE6 showing certain details of the thread severing mechanism;

FIGURE 9 is :an enlarged vertical sectional view taken through thethroat plate and slider structure as would be seen when viewed along theline 99 of FIGURE 8;

FIGURE 10 is a bottom plan view of the heatable wire carrying throatplate and slider illustrating the aligned positions thereof as during anormal stitching operation;

FIGURE 11 is similar to the showing of FIGURE 10 excepting that thethread shifting slider is illustrated in shifted position correspondingto that for thread severing by thread displacement against the heatablewire;

FIGURE 12 is a top plan view of the throat plate and slider assemblyaligned as shown in the bottom plan view of FIGURE 10;

FIGURES 13 and 14 are enlarged vertical sectional views taken throughthe throat plate in the same manner as seen in FIGURE 8 with two pliesof fabric being stitched, FIGURE 13 illustrating the relative positionsof needle and slider device during stitching, while FIGURE 14 shows therelative positions during thread severing; and

FIGURE 15 illustrates in schematic form the electrical circuitryassociated with the thread trimming device for actuating the same undercontrol of the sewing machine operator.

In the several figures, like elements are denoted by like referencecharacters.

Turning to an examination of the figures, there is seen in FIGURES 1 to4 a sewing machine head designated generally as provided with aplurality of thread guides 21 through 26, thread tensioner 27, threadtake-up lever 28, needle bar 29 carrying needle 30 through which isthreaded in usual fashion -a thread 31. Disposed behind the needle bar29 is the presser foot bar 32 carrying presser foot 33 shown inoperative position seated downward upon the feed dogs projecting upwardthrough the throat plate 34 of the sewing machine. The throat plate 34is clip engaged to the sewing machine bed plate 35 below which isoperatively mounted in the usual manner the bobbin 36. The presence ofall of the foregoing described elements in a sewing machine isconventional, but the specific structure of the throat plate 34 is notconventional and incorporates therein the electrically energizable hotwire thread cutting means for severing the needle thread and the bobbinthread. Before describing the additional mechanism associated with thethroat plate for energizing and actuating the thread cutting device perse, it will be conducive to a more complete understanding of theinvention to first examine the mode of operation of the entireapparatus.

Operation of the apparatus is best understood by referring to FIGURES 1,2, 13 and 14 of the drawings and involves the inter-relationships of thethread take-up 28, needle 30 and bobbin 36. FIGURE 13 illustrates theneedle 30 in its down position where it has passed through upper andlower plies of cloth 37 and 38, through the needle hole 39 in the throatplate 34 and through an underlying aligned hole 40 in :a thread shiftingmeans slider device 41 to be described hereinafter, and has thrown out aneedle thread loop 42 about to be caught by the hook point of the bobbin36 for the purpose of stitch forming with the bobbin thread 43.

It should be noted that the sewing machine is not motionless but is inthe process of stitch formation and the sequence of events now beingdescribed involves proper timing of the sewing machine stitch formingcycle with actuation of the thread severing mechanism in the mannerbeing now set forth. At this point of the operation the needle 30 hasjust started to rise but the needle thread 31 does not rise with itsince the loop 42 has been engaged by the bobbin hook and is beingcarried down and around the bobbin, the needle thread being loose atthis point so as to be pulled by the bobbin hook due to the fact thatthe thread take-up 28 is moving downward. The needle 30 continues torise upward and out of the throat plate and fabric toward its upperposition, the bobbin has interlooped the needle thread 31 with thebobbin thread 43, and the thread take-up 28 has reached the bottom ofits travel and is about to start upward.

As the thread tage-up 28 starts upward it immediately begins to shortenthe needle thread loop 42 which has been substantially enlarged by thecasting operation of the bobbin so that this enlarged loop 42 begins todecrease in size and effectively move upward toward the throat plate 34.The needle 30 is still moving upward and the sewing machine feed dogsare starting to advance the plies being stitched for the next stitchlength. At this part of the cycle the needle 30 is substantially at thetop of its stroke and the thread take-up 28 has brought the needlethread loop 42 upward so that it is approximately of the size shown inFIGURE 13 although it will be understood that the showing of FIGURE 13should be viewed as though the needle 30 were absent therefrom.

The timing of the apparatus is such that the throat plate slider 41 isnow quickly shifted, as shown by the arrow 44 in FIGURE 14, to carry theneedle thread loop 42 and bobbin thread 43 against the heatable wire 45which is at that time deenergized so that the threads are held by theslider 41 and heatable wire 45. Simultaneous with this movement of theslider 41, the needle thread tensioner 27 is disengaged from the needlethread 31 by operation of the tension release device 46 so that theupwardly moving needle thread take-up 28 pulls thread through the openedtensioner 27 from the needle thread supply. Needle thread tensionrelease and holding of the threads in the throat plate by the slider 41is maintained until the thread take-up 28 reaches the top of its stroketo thereby draw all of the thread that is required for formation of thenext stitch.

At this point in the cycle, the sewing machine needle has just startedto descend and the sewing machine apparatus is brought to a stop. Thetension release device 46 is now deactuated to reapply the threadtensioner 27 to the needle thread 31, and the heatable wire 45 in thethroat plate 34 is energized to sever the needle thread and bobbinthread held thereagainst by the slider 41. The wire 45 is nowdeenergized and the throat plate slider 41 is shifted back to theposition shown in FIGURE 13 with its aperture 40 in vertical alignmentwith the throat plate needle hole 39.

From the foregoing description and an examination of FIGURE 14 it isobserved that the thread severing operation 'has been completed in suchmanner as to leave a very short thread tail extending downward from thelower ply 38, on the order of half a stitch length, and at the same timeall of the thread necessary to form the next stitch has been drawn fromthe needle thread supply so that initiation of the next sewingoperation. does not unthread the needle 30. Moreover, the needle 30 issubstantially at its upper position so that the stitched work may beeasily removed and new work placed in stitching position.

Understanding now the operation of the apparatus according to theinvention, consider now FIGURES 1 to 5 which illustrate the portion ofthe apparatus operative to release the tension on the needle thread 31as previously described, after which the throat plate thread severingportion of the apparatus and the electrical circuitry for providing thenecessary timed operation will be described.

As best seen in FIGURES 3 and 5, a cam 47 provided with a slot 48 ismounted upon for rotation with the drive shaft 49 of a rotary solenoid50 which is itself fixedly mounted by studs 51 to the backplate 52 ofthe tension release device support frame. Projecting into cam slot 4-8is a cam follower stud 53 fixedly secured to the upper end of a crankarm. 54 which has its lower end fixedly secured to a transverselyextending crank shaft 55 by means of a lock screw 56, the crank shaft 55extending forward to the front of the sewing machine head through thearms of a U-shaped bearing block 57 as best seen in the showing ofFIGURE 5. The forward end of crank shaft 55 is provided with a slottedfront face 'keyway 58 within which is disposed the arm 59 of the needlethread tension release member 60 which terminates at its forward end inan upturned hook 61, the tension release member 60 being locked to thecrank shaft 55 by means of the end screw 62. As best seen in FIGURE 1,the upturned hook '61 of the tension release member 60 is so positionedas to normally not interfere with the operation of the thread tensioner27, but it will be appreciated that when the hook 61 swings upwardbetween the plates of the thread tensioner it causes the latter to moveaway from one another and to thereby release the tension upon the needlethread 31.

The motion of the tension release hook 61 is effected by actuation ofrotary solenoid 50 to rotate its shaft 49 and the aforedescribed cam 47mounted thereon. The slot 48 of the cam 47 causes the cam follower stud53 to rotate the crank arm 54- and crank shaft 55 to cause the tensionrelease hook 61 to release tension of the needle thread 31. Deactuationof solenoid 50 allows the tension release hook 61 to rotate downward toits normal disengaged position from the thread tensioner 27 to therebyreestablish normal engagement of the tensioner with the needle thread.Actuation and deactuation of the rotary solenoid 50 is effected byelectrical energization and deenergization of the solenoid via suitableelectrical conductors connected to the plug 63 carried by insulatingblock 64.

The frame to which all of the previously described operative parts ofthe needle thread cutting mechanism are secured is disposed upon thesewing machine head 20 as best seen in the showings of FIGURES 1 to 5 sothat the frame top plate 65 overlies the sewing machine head with thestud 66 disposed within the slot 67 to thereby lock the frame with theplate 68 and machine screws 69. Projecting transversely from rear tofore end of the frame immediately beneath the top plate 65 and above theU- shaped bearing block 57 is the bar 70. Secured to the front end ofthe bar 70 and bearing block 57 by means of the socket head bolts 71 isa curved clamp bar 72 about the center of which is disposed a pressurepad 73 adjustably shiftable toward or away from the head carrying arm ofthe sewing machine by means of the adjusting bolt 74.

Understanding now the portion of the apparatus for 6 releasing tensionon the needle thread of the sewing machine, now consider that part ofthe apparatus which is operative to sever the needle and bobbin threadsof the sewing machine. This portion of the apparatus is illustrated incombination with the sewing machine in FIGURE 2 and is separatelyillustrated in the showings of FIGURES 6 to 14. As best seen in theshowing of FIGURE 2 the sewing machine is provided with a cylindricalstud 75 secured to and extending downward from the bed plate 35 uponwhich is mounted the unit 76 which conjointly with the structure of thethroat plate 34 comprises the thread cutting mechanism. As best seen inFIGURES 6 and 8, the 'unit 76 includes a mounting block 77 verticallybored as at 78 so that the unit may be slipped onto the stud 75 andfixedly secured in position thereon by means of the locking screw 79.Disposed upon opposite sides of the mounting block 106 and extendingtoward the bobbin 36 are a pair of side plates designated respectivelyas 80 and 81,. the side plate 80 being secured to the mounting block 77as by means of the screws 82 and the side plate 81 being similarlysecured to the mounting block 77 by means of screws '83.

Fixedly secured to the lower edge of side plate 80 is an insulatingterminal board 84 which carries two sets of electrical contact plugprongs designated respectively as 85 and 86. Also mounted to the sideplate 80 is the rotary solenoid 87 effective to clockwise rotate theupper end of lever 88 about pivot 89 through the intervening links 90and 91. Such rotation of lever 88 occurs when the rotary solenoid 87 isactuated by energization via its conductor leads 92 which areelectrically connected to plug prongs 85. As best seen in FIGURES 8 and9 an insulator block 93 is secured to side plate 81 as by means of themachine screws 94, the insulator block carrying a pair of contactsleeves 95 electrically energizable via electrical conductors 96 theopposite ends of which connect to plug prongs 86 mounted upon terminalboard 84.

Secured to the underside of the throat plate 34 is an insulator terminalblock 97 carrying a pair of plug prongs 98 seatable downward into thecontact sleeves 95 carried by the side plate 81. The prongs 98 haveextending therefrom electrical conductors 99 which feed respectivelyinto a pair of ceramic insulating sleeves 100 and close through aresistance wire element 45 which has been previously mentioned inconnection with the showings of FIGURES 13 and 14. The ceramic sleeves100 are cemented into a recess cut upward from the underside of thethroat plate 34 so as to position the resistance wire element 45immediately adjacent to the throat plate needle hole 39 with the sleeves100 lying between the normally existing feed dog slots as for exampleillustrated at 101 and 102.

Underlying the throat plate 34 is a generally U-shaped slider element 41having a thin arm 103 extending parallel to and between the half feeddog slot 102 and one of the full slots 101, and a wide arm 104 having aturned up outer side edge 105 which abuts the straight side 106 of thethroat plate 34. The slider arm 104 is slotted as at 107, the screws 108projected therethrough into the throat plate holding the slider captiveand in proper position. The end of thin arm 103 terminates in threadshifter 109 centrally apertured at 40 as previously described, theaperture 40 being colinear with the throat plate needle hole 39 duringstitching. Slider arm 104 is provided at its end connected to the sliderarms bridging part 110 with an ear 111 having an aperture 112therethrough within which the upper end of lever 88 is adapted fordisposition to shift the slider 41 and cause the thread shifter 109 toshift the bobbin thread 43 and needle thread loop 42 over against theresistance wire element 45 carried by the insulating sleeves 100 and tothereby sever the threads when the resistance wire element is in aheated state.

Operation of the thread cutting system according to the invention iscarried out automatically in combination with operation of an automaticneedle positioning mechanism which causes the sewing machine needle torise to its upper position. A suitable automatic needle positioningmechanism for this purpose is .described in US. Patent No. 2,961,591entitled Automatic Needle Positioning Mechanism. Operation of the threadsevering mechanism as has hereinbefore been described may be effected byelectrical circuitry as illustrated in the showing of FIGURE of thedrawings to which reference should now be made.

Power for operation of the thread severing apparatus is supplied by asource of alternating current through conductors 113 and 114 whichconnect to the primary windings 115 and 116 of a transformer 117 havingsecondary windings .118 and 119. Connected across primary winding 115 isa bridge rectifier circuit 120 which supplies energizing current to coil50a of rotary solenoid 50 through switch 121 when the latter is closed.Secondary winding 118 supplies energizing current through a fullwaverectifier 122 to coil 87a of rotary solenoid 87 through switch 123 whenthe latter is closed, the energizing current magnitude being controlledby the setting of series connected rheostat 124. The contact switches121 and 123 are protected by are suppression circuits v125 and 126connected respectively thereacross.

Secondary winding 119 provides alternating current to the threadsevering heatable wire 45 through a series connected control rheostat127 and relay contacts 128 which latter is controlled by energizationand deenergization of relay coil 129. The energization of relay coil 129is effected by alternating current picked off from transformer primarywinding 115 and applied through switch 130 when the latter is closed.Energization of the needle positioning mechanism used in combinationwith the thread trimming apparatus is controlled by switch 132 whichcompletes the needle positioning energization circuit via conductors133. Initiation of the entire thread trimming operation is controlled bythe closure of momentary make switch 134 which energizes the winding.135 of motor 136 which is connected across primary winding 116. Motor136 is a timer motor having an output shaft upon which are mounted forrotation therewith a series of five cams designated 137 through 141,these cams being mounted to respectively operate in the desired timesequence the switches 142, 121, 123, .130 and 131.

Switch 132 is a part of the treadle switch structure described in thepreviously referred to US. Patent 2,961,- 591, this switch being closedonly when the sewing machine treadle has been released to terminate astitching operation with the sewing machine needle in its .down positionunder control of the needle positioning mecha nism.

Switch 134 closes the circuit through motor winding 135 to initiaterotation of the motor 136. Cam 137 transfers the pole of switch 142 tobypass switch .134 and provide a holding circuit which maintains themotor winding 135 energized so that the cams continue to rotate. Switch143 closes simultaneously with switch 134 and completes a circuitthrough conductors 144 to initiate the upward movement of the sewingmachine needle. Cam 141 next closes switch 131 so that the needlepositioner is energized through conductors 133 to provide an interlockbetween the needle positioner and the thread trimmer during the trimmingcycle. At the proper time during operation of the needle positioner, ashas previously been explained, cams 138 and 139 close switches 121 and123 to energize the solenoids 50 and 87 to thereby release the needlethread tensioner from the needle thread and actuate throat plate slider41. Cam 138 opens switch 121 to deenergize rotary solenoid 50 andreapply the thread tensioning device to the needle thread. Cam 140 nowcloses switch 130 to deenergize solenoid coil 129 and close switch 128which energizes heatable wire 45 to thereby sever the needle and bobbinthreads. Cam 140 then opens switch 130 to deenergize severing wire 45,after which cam 139 opens switch 123 to deenergize rotary solenoid 87and retract throat plate slider 41. Cam 137 now opens switch 142 whichbreaks the holding current circuit for the motor 136 and causes themotor to stop so that the circuit conditions are again as illustratedwith the exception that the treadle interlock switch 132 remains closeduntil a new stitching operation is commenced.

Having now described our invention in connection with a particularlyillustrated embodiment thereof, it will be appreciated thatmodifications and variations of this invention may now occur from timeto time to those persons normally skilled in the art without departingfrom the essential scope or spirit of the invention, and accordingly itis intended to claim the same broadly as well as specifically asindicated by the appended claims.

What is claimed as new and useful is:

1. In combination with a sewing machine having, a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stitches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movements of said needle and looper todraw the formed stitches up into the work as aforesaid and to thereafterdraw thread through said tensioner from a needle thread supply to formthe next stitch, the combination comprising,

(a) an electrically energizable heat generating element disposed beneaththe throat plate immediately adjacent to the throat plate needle holeand effective when energized to burn through threads contacting thesame, and

(b) thread shifting means disposed beneath the throat plate in suchpositional relationship to said electrically energizable heat generatingelement that said thread shifting means is operative when actuated tofrictionally snub both the interlooped needle thread and bobbin threadaround and between said thread shifting means and said electricallyenergizable heat generating element.

2. In combination with a sewing machine having, a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stitches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movements of said needle and looper todraw the formed stitches up into the work as aforesaid and to thereafterdraw thread through said tensioner from a needle thread supply to formthe next stitch, the combination comprising,

(a) an electrically energizable heat generating element carried by thethroat plate on the underside thereof immediately adjacent to the throatplate needle hole and effective when energized to burn through threadscontacting the same, and

(b) thread shifting means carried by the throat plate on the undersidethereof in such positional relationship to said electrically energizableheat generating element that said thread shifting means is operativewhen actuated to frictionally snub both the interlooped needle threadand bobbin thread around and between said thread shifting means and saidelectrically energizable heat generating element.

3. The apparatus as set forth in claim 2 wherein the throat plateincludes a plurality of parallel feed dog slots and said thread shiftingmeans comprises, a generally U- shaped slider device disposed againstthe underside of the throat plate and shiftable laterally with respectthereto in opposite directions parallel to the longitudinal extent ofthe throat plate feed dog slots, one arm of said U- shaped slider beingrelatively thin and extending longitudinally between an adjacent pair ofthroat plate feed dog slots and terminating at its free end in a threadshifter end formation disposed immediately adjacent to the throat plateneedle hole, the other arm of said slider including slider guide meansdisposed in abutment against a straight side edge of the throat plate,and means holding said slider captive to said throat plate.

4. In combination with a sewing machine having, a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stitches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movements of said needle and looper todraw the formed stitches up into the work as aforesaid and to thereafterdraw thread through said tensioner from a needle thread supply to formthe next stitch, the combination comprising,

(a) an electrically energizable heat generating element disposed beneaththe throat plate immediately adjacent to the throat plate needle holeand effective when energized to burn through threads contacting thesame,

(b) thread shifting means disposed beneath the throat plate in suchpositional relationship to said electrically energizable heat generatingelement that said thread shifting means is operative when actuated tofrictionally snub both the interlooped needle thread and bobbin threadaround and between said thread shifting means and said electricallyenergizable heat generating element,

(c) needle thread tension release means operative when actuated todisable the said needle thread tensioner to remove tension on the needlethread, and operative when deactuated to restore needle thread tension,

(d) first selectively operable control means for moving the take-up armupward and the needle upward out of the throat plate to draw theinterlooped needle thread and bobbin thread upward toward the work beingstitched and for drawing thread from the needle thread supply, and

(e) second selectively operable control means elfective when operated toactuate and deactuate said thread shifting means and tension releasemeans and en ergize and deenergize said heat generating element in timedrelation to one another and to the positions of the thread take-up armand needle as determined by said first control means so that saidinterlooped needle thread and bobbin thread are held below the throatplate by said thread shifting means while the take-up arm draws threadfor the next stitch from the needle thread supply through the threadtensioner disabled by said tension release means, and thereafter theheld threads are severed by energization of said heat generatingelement.

5, In combination with a sewing machine having, a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stitches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movements 10 of said needle and looper todraw the formed stitches up into the work as aforesaid and to thereafterdraw thread through said tensioner from a needle thread supply to formthe next stitch, the combination comprising,

(a) an electrically energizable heat generating element carried by thethroat plate on the underside thereof 'immediately adjacent to thethroat plate needle hole and effective when energized to burn throughthreads contacting the same,

(b) thread shifting means carried by the throat plate on the undersidethereof in such positional relationship to said electrically energizableheat generating element that said thread shifting means is operativewhen actuated to frictionally snub both the interlooped needle threadand bobbin thread around and between said thread shifting means and saidelectrically energizable heat generating element,

(c) needle thread tension release means operative when actuated todisable the said needle thread tensioner to remove tension on the needlethread, and operative when deactuated to restore needle thread tension,

(d) first selectively operable control means for moving the take-up armupward and the needle upward out of the throat plate to draw theinterlooped needle thread and bobbin thread upward toward the work beingstitched and for drawing thread from the needle thread supply, and

(e) second selectively operable control means effective when operated toactuate and deactuate said thread shifting means and tension releasemeans and energize and deenergize said heat generating element intimedrelation to one another and to the positions of the thread take-uparm and needle as determined by said first control means so that saidinterlooped needle thread and bobbin thread are held below the throatplate by said thread shifting means while the take-up arm draws threadfor the next stitch from the needle thread supply through the threadtensioner disabled by said tension release means and thereafter the heldthreads are severed by energization of said heat generating element.

6. In combination with a sewing machine having, a

throat plate provided with a needle hole therethrough, a reciprocatingneedle cyclically carrying a needle thread upward above the throat plateand downward therebelow through the needle hole in the throat plate, aneedle thread tensioner, a rotating looper below the throat platecarrying a bobbin thread operative to pick up the needle thread andinterloop the same with the bobbin thread to form lock stitches drawableupward into work disposed on the throat plate, an oscillating needlethread take-up arm moving in synchronism with the movements of saidneedle and looper to draw the formed stitches up into the work asaforesaid and to thereafter draw thread through said tensioner from aneedle thread supply to form the next stitch, the combinationcomprising,

(a) an electrically energizable heat generating element carried by thethroat plate on the underside thereof immediately adjacent to the throatplate needle hole and effective when energized to burn through threadscontacting the same,

('b) thread shifting means carried by the throat plate on the undersidethereof in such positional relationship to said electrically energizableheat generating element that said thread shifting means is operativewhen actuated to frictionally snub both the interlooped needle threadand bobbin thread around and between said thread shifting means and saidelectrically energiza'ble heat generating element,

(c) electrically energizable actuating means coupled to said threadshifting means operative when energized to actuate said thread shiftingmeans and operative when deenergized to deactuate said thread shiftingmeans,

(d) needle thread tension release means carried by the sewing machineand operative when actuated to disable the said needle thread tensionerto remove tension on the needle thread, and operative when deactuated torestore needle thread tension,

(e) first selectively operable control means for moving the take-up armupward and the needle upward out of the throat plate to draw theinterlooped needle thread and bobbin thread upward toward the work beingstitched and for drawing thread from the needle thread supply, and

(f) second selectively operable control means effective when operated toactuate and deactuate said thread shifting means and tension releasemeans and energize and deenergize said heat generating element in timedrelation to one another and to the positions of the thread take-up armand needle as determined by said first control means so that saidinterlooped needle thread and bobbin thread are held below the thnoatplate by said thread shifting means while the take-up arm draws threadfor the next stitch from the needle thread supply through the threadtensioner disabled by said tension release means, and thereafter theheld threads ar severed by energization of said heat generating element.

7. In combination with a sewing machine having a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stitches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movements of said needle and looper todraw the formed stitches up into the work as aforesaid and to thereafterdraw thread through said tensioner from a needle thread supply to formthe next stitch, and an automatic needle positioning deviceautomatically operative to position the needle in its down position atthe end of a stitching operation and including selectively actuatableposition control means operative when actuated to raise the sewingmachine take-up arm to its maximum upward position, the combinationcomprising,

(a) an electrically energizable heat generating element disposed beneaththe throat plate immediately adjacent to the throat plate needle holeand effective when energized to burn through threads contacting thesame,

(b) thread shifting means disposed beneath the throat plate in suchpositional relationship to said electrically energizable heat generatingelement that said thread shifting means is operative when actuated tofrictionally snub both the interlooped needle thread and bobbin threadaround and between said thread shifting means and said electricallyenergizable heat generating element,

(0) needle thread tension release means operative when actuated todisable the said needle thread tensioner to remove tension on the needlethread, and operative when deactuated to restore needle thread tension,and

(d) selectively operable control means elfective when operated toactuate and deactuate said needle positioning device position controlmeans and said shifting means and tension release means and energize anddeenergize said heat generating element in automatically timed relationto one another so that said interlooped needle thread and bobbin threadare held below the throat plate by said thread shifting means while thetake-up arm draws thread for the next stitch from the needle threadsupply through the thread tensioner disabled by said tension releasemeans and thereafter the held threads are severed by energization ofsaid heat generating element.

8. In combination with a sewing machine having a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stitches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movement of said needle and looper todraw the formed stitches up into the work as aforesaid and to thereafterdraw thread through said tensioner from a needle thread supp-1y to formthe next stitch, and an automatic needle positioning deviceautomatically operative to position the needle in its down position atthe end of a stitching operation and including selectively actuatableposition control means 0perative when actuated to raise the sewingmachine take up arm to its maximum upward position, the combinationcomprising,

(a) an electrically energizable heat generating element disposed beneaththe throat plate immediately adjacent to the throat plate needle holeand efiiective when energized to burn through threads contacting thesame,

(b) thread shifting means disposed beneath the throat plate in suchpositional relationship to said electrically energizable heat generatingelement that said thread shifting means is operative when actuated tofrictionally snub both the interlooped needle thread and bobbin threadaround and between said thread shifting means and said electricallyenergizable heat generating element,

(c) needle thread tension release means operative when actuated todisable the said needle thread tensioner to remove tension on the needlethread, and operative when deactuated to restore needle thread tension,and

(d) selectively operable control means effective when operated to renderoperative said needle positioning device position control means, saidthread shifting means and tension release means, and said threadsevering heat generating element in automatically timed relation to oneanother, whereby,

(1) said needle positioning device is activated to move the needlethread take-up arm upward toward its topmost position,

(2) said tension release means and thread shifting means are actuatedwhile the take-up is moving upward at a time before the interloopedneedle thread and bobbin thread are drawn up above the underside of thethroat plate so that the threads are snubbed as aforesaid and the needlethread tensioner is disabled,

(3) the take-up arm continues to move to its topmost position and drawsthread from the needle thread supply through the disabled tensioner, theneedle positioner being then deactivated,

(4) said tension release means is deactuated and said heat generatingelement is energized to burn through both the needle thread and bobbinthread,

(5) said heat generating element is deenergized and said thread shiftingmeans is deactuated,

9. In combination with a sewing machine having, a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stitches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movements of said needle and looper todraw the formed stitches up into the Work as aforesaid and to thereafterdraw thread through said tensioner from a needle thread supply to formthe next stitch, and an automatic needle positioning deviceautomatically operative to position the needle in its down position atthe end of a stitching operation and including selectively actuatableposition control means operative when actuated to raise the sewingmachine takeup arm to its maximum upward position, the combinationcomprising,

(a) an electrically energizable heat generating element carried by thethroat plate on the underside thereof immediately adjacent to the throatplate needle hole and effective when energized to burn through threadscontacting the same,

(b) thread shifting means carried by the throat plate on the undersidethereof in such positional relationship to said electrically energizableheat generating element that said thread shifting means is operativewhen actuated to frictionally snub both the interlooped needle threadand bobbin thread around and between said thread shifting means and saidelectrically energizable heat generating element,

(c) electrically energizable actuating means coupled to said threadshifting means operative when energized to actuate said thread shiftingmeans and operative when deenergized to deactuate said thread shiftingmeans,

(d) needle thread tension release means carried by the sewing machineand operative when actuated to disable the said needle thread tensionerto remove tension on the needle thread, and operative when deactuated torestore needle thread tension, and

(e) selectively operable control means effective when operated toactuate and deactuate said needle positioning device position controlmeans and said thread shifting means and tension release means andenergize and deenergize said heat generating element in automaticallytimed relation to one another so that said interlooped needle thread andbobbin thread are held below the throat plate by said thread shiftingmeans while the take-up arm draws thread for the next stitch from theneedle thread supply through the thread tensioner disabled by saidtension release means and thereafter the held threads are severed byenergization of said heat generating element.

10. In combination with a sewing machine having, a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stitches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movements of said needle and looper todraw the formed stitches up into the work as aforesaid and to thereafterdraw thread, through said tensioner from a needle thread supply to formthe next stitch, and an automatic needle positioning deviceautomatically operative to position the needle in its down position atthe end of a stitching operation and including selectively actuatableposition control means operative when actuated to raise the sewingmachine take-up arm to its maximum upward position, the combinationcomprising,

(a) an electrically energizable heat generating element carried by thethroat plate On the underside thereof immediately adjacent to the throatplate needle hole and effective when energized to burn through threadscontacting the same,

(b) thread shifting means carried by the throat plate on the undersidethereof in such positional relationship to said electrically energizableheat generating element that said thread shifting means is operativewhen actuated to frictionally snub both the interlooped needle threadand bobbin thread around and between said thread shifting means and saidelectrically energizable heat generating element,

(c) electrically energizable actuating means coupled to said threadshifting means operative when energized to actuate said thread shiftingmeans and operative when deenergized to deactuate said thread shiftingmeans,

(d) needle thread tension release means carried by the sewing machineand operative when actuated to disable the said needle thread tensionerto remove tension on the needle thread, and operative when deactuated torestore needle thread tension, and

(e) selectively operable control means effective when operated to renderoperative said needle positioning device position control means, saidthread shifting means and tension release means, and said threadsevering heat generating element in automatically timed relation to oneanother, whereby,

(1) said needle positioner is activated to move the needle threadtake-up arm upward toward its topmost position,

(2) said tension release means and thread shifting means are actuatedwhile the take-up is moving upward at a time before the interloopedneedle thread and bobbin thread are drawn up above the underside of thethroat plate so that the threads are snubbed as aforesaid and the needlethread tensioner is disabled,

(3) the take-up arm continues to move to its topmost position and drawsthread from the needle thread supply through the disabled tensioner, theneedle positioner being then deactivated,

(4) said tension release means is deactuated and said heat generatingelement is energized to burn through both the needle thread and bobbinthread,

(5 said heat generating element is deenergized and said thread shiftingmeans is deactuated.

11. The apparatus as set forth in claim 10 wherein the throat plateincludes a plurality of parallel feed dog slots and said thread shiftingmeans comprises, a generally U- shaped slider device disposed againstthe underside of the throat plate and shiftable laterally with respectthereto in opposite directions parallel to the longitudinal extent ofthe throat plate feed dog slots, one arm of said U-shaped slider beingrelatively thin and extending longitudinally between an adjacent pair ofthroat plate feed dog slots and terminating at its free end in a threadshifter end formation disposed immediately adjacent to the throat plateneedle hole, the other arm of said slider including slider guide meansdisposed in abutment against a straight side edge of the throat plate,and means holding said slider captive to said throat plate.

12. In combination with a sewing machine having, a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stitches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movements of said needle and looper todraw the formed stitches up into the work as :aforesaid and tothereafter draw thread through said tensioner from a needle threadsupply to form the next stitch, the combination comprising,

(a) an electrically energizable heat generating element carried by thethroat plate on the underside thereof immediately adjacent to the throatplate needle hole and effective when energized to burn through threadscont-acting the same,

(b) thread shifting means carried by the throat plate on the undersidethereof in such positional relationship to said electrically energizableheat generating element that said thread shifting means is operativewhen actuated to frictionally snub both the interlooped needle threadand bobbin thread around and between said thread shitting means and saidelectrically energizable heat generating element, and

(c) needle thread tension release means carried by the the sewingmachine and operative when actuated to disable the said needle threadtensioner to remove tension on the needle thread, and operative whendeactuated to restore needle thread tension.

13. In combination with a sewing machine having a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stitches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movements of said needle and looper todraw the formed stitches up into the work as aforesaid land tothereafter draw thread through said tensioner from a needle threadsupply to form the next stitch, and an automatic needle positioningdevice automatically operative to position the needle in its downposition at the end of a stitching operation and including selectivelyactuatable position control means operative when actuated to raise thesewing machine take-up arm to its maximum upward position, thecombination comprising,

(a) an electrically energizable heat generating element disposed beneaththe throat plate immediately adjacent to the throat plate needle holeand etfective when energized to burn through threads contacting thesame,

(b) thread shifting means disposed beneath the throat plate in suchpositional relationship to said electrically energizable heat generatingelement that said thread shifting means is operative when actuated tofrictionally snub both the interlooped needle thread and bobbin threadaround and between said thread shifting means and said electricallyenergizable heat generating element, and

(c) needle thread tension release means operative when actuated todisable the said needle thread tensioner to remove tension on the needlethread, and operative when deactuated to restore needle thread ten- 14.In combination with a sewing machine having, a throat plate providedwith a needle hole therethrough, a reciprocating needle cyclicallycarrying a needle thread upward above the throat plate and downwardtherebelow through the needle hole in the throat plate, a needle threadtensioner, a rotating looper below the throat plate carrying a bobbinthread operative to pick up the needle thread and interloop the samewith the bobbin thread to form lock stiches drawable upward into workdisposed on the throat plate, an oscillating needle thread take-up armmoving in synchronism with the movements of said needle and looper todraw the formed stitches up into the work as aforesaid and to thereafterdraw thread through said tensioner from a needle thread supply toformthe next stitch, and an automatic needle positioning deviceautomatically operative to position the needle in its down position atthe end of a stitching operation and including selectively actuatableposition control means operative when actuated to raise the sewingmachine take-up arm to its maximum upward position, the combinationcomprisa (a) an electrically energizable heat generating element carriedby the throat plate on the underside thereof immediately adjacent to thethroat plate needle hole and effective when energized to burn throughthreads contacting the same, 4

(b) thread shifting means carried by the throat plate on the undersidethereof in such positional relationship to said electrically energizableheat generating element that said thread shifting means is operativewhen actuated to frictionally snub both the interlooped needle threadand bobbin thread around and between said thread shifting means and saidelectrically energizable heat generating element,

(c) electrically energizable actuating means coupled to said threadshifting means operative when energized to actuate said thread shiftingmeans and operative when deenergized to deactuate said thread shiftingmeans, and

(d) needle thread tension release means carried by the sewing machineand operative when actuated to disable the said needle thread tensionerto remove tension on the needle thread, and operative when deactuated torestore needle thread tension.

References Cited UNITED STATES PATENTS 1/ 1964 Schenkengel 112-2527/1965 Chudner 112--252

